Means for controlling the level of liquid in dishwashing machines



Nov. 13, 1951 s. B. F. CARLSTEDT MEANS FOR CONTROLLING THE LEVEL OF LIQUID IN DISHWASHING MACHINES Filed Aug. 24, 1948 lNVENTOR SVEN BORJE FREDRIC CARLSTEDT ATTORNEY Petented Nov. 13, 1951 UNITED, STATES PATENT OFFICE MEANS FOR CONTROLLING THE LEVEL OF LIQUID IN DISHWASHING MACHINES Sven Biirie Fredrik Carlstedt, Stockholm, Sweden Application August 24, 1948, Serial No. 45,808

' 6 Claims. (Cl. 134-51) The invention relates to dish-washing machines, other washing machines, and the like apparatus which in their lower part near the bottom have rotatable elements and an inlet for liquid-adapted to be opened when the machine is put into operation so that the lower part of the machine successively is filled with liquid.

Machines of this type have hitherto usually been provided with a manually operated tap .to open the inlet conduit in question latest on the beginning of the washing operation and to close the same when the required amount of liquid is accumulated in the lower part of the machine. Sometimes an overflow has been arranged at a suitable place in the wall of said lower part whereby it was rendered superfluous to close the inlet under the washing operation.

When the machine is in operation, the liquid in the lower part of the machine is circulated by the rotatable elements and thrown upwards into the upper part of the machine so that the goods to be washed and placed on a suitable support in said upper part are subjected to a powerful spouting.

One of the objects of the invention is to provide inlet control means which automatically stop the supply of liquid as soon as the lower part of the machine has been filled with the required amount of liquid.

Another object of the invention is to provide means permitting an adjustment of the liquid level on the reaching of which the stopping of the liquid supply is brought about, i. e. an adjustment of the amount of liquid accumulated in the lower part of the machine at the moment when the supply of liquid is broken by the inlet control means.

Further objects and advantages of the invention will be apparent from the following description of a preferred embodiment of the invention considered in connection with the accompanying drawing which forms part of this sepeciflcation and of which:

Fig. 1 is an end-elevation, partly in section, of a dish-washing machine according to the invention;

In Sweden December 8, 1946 ing has an upper part I and a lower part 2. The upper part i which preferably has a square horizontal cross-section and rectangular side walls made of a water-tight material such as thin sheet-plate, is covered by a lid 3 and contains a basket 4 for dishes to be cleaned, for example plates 5. The lower part 2, the side walls and bottom portion of which preferably also consist of a water-tight material such as sheet-plate and which is of an oblong shape and quite open at its top towards the upper part I, is passed by a shaft 8. Said shaft may extend through said part 2 vertically from the top of this latter to the bottom thereof and be provided with screw blades working axially. In the embodiment illustrated, however, the shaft 6 extends horizontally and carries a number of impeller members such as shovels I which work radially. Each of theseshovels may extend over the whole length of the shaft within the lower part 2. In the example of execution illustrated in the drawing, however, there are three shovels I of togther one total shaft length uniformly disposed round the circumference. Each shovel I is balanced by a counter-balance 8. The shaft 6 is rotatably mounted in bushings 9 located in elastic pedestal bodies l0 disposed at each end of the end walls Fig. 2 is a corresponding side-elevation, partly in vertical longitudinal section;

Fig. 3 is a vertical longitudinal section, on an enlarged scale, through the lower part on the right of Fig. 2; and

Fig. 4 is a diagram showing aresistance control arranged in the current circuit of a driving electric motor of the dish-washing machine.

The dish-washing machine shown in the drawof the lower part 2, said pedestal bodies being secured to the end walls by means of caps II and I2, respectively. One end of the shaft 6 extends outside the wall of the lower part 2 and carries a pulley l3 which may be driven by means of a belt H from an electric motor l5 adapted for direct as well as alternating current. Said electic motor is of a type the number of revolutions of which varies in accordance with the load on the elements driven by it, preferably a series. motor.

The shaft 6 has a central channel It opening towards the cap I2 which is provided with a recess I! to which a liquid supply conduit (not shown) can be attached. A collar packing l8 surrounds the end of the shaft 6 and abuts against a surface enclosing the said packing and arranged in the cap l2. At the bottom of the lower part 2 is a drain I9 controlled by a valve 20.

The channel It communicates with the interior of the lower part 2 through a channel 2|, 22 which is controlled by a valve 23 normally closed by a compressionspring 24 from the one side and opened by a centrifugal body 25 from the other side. The valve body 23 may be made in one piece with the body 25, as is assumed in the present case, but it may also be a separate counter-balance I consists of a radially extending valve housing secured to a sloove l" mounted on and extending parallelly with the shaft 4, to which said sleeve 2" is secured by radial bolts 2". The sleeve 2" also carries the appendant shovel I. The centrifugal body 25 is arranged to slide as a piston within the houstlng 2'. The spring 24 is fixed between said centrifugal body 25 and a bolted cap 26 lockable by a lock-nut 21. The channel mentioned above comprises on the one part the radial hole 2| in the shaft 8 which connects the central channel I! in the shaft 2 with the housing 8 which is quite open towards the exterior surface of the shaft, and on the other part the hole 22 in the wall of the housin 8' which hole connects the interior of said housing with the space outside the same, i. e. with the interior of the lower part 2 of the dish-washing machine. The centrifugal body 25 carries on its end facing the shaft 6 the specific valve body 22 which tightens against a seat surrounding the hole 2| in said shaft and which may be made of a material particularly suitable for this purpose. for example rubber. The elements 2, 23, 24, 25, 26, and 21 are together given a weight that balances the weight of the appendant shovel I.

The driving motor IS, the spring 24 and the centrifugal element 23, 25 are constructed so as to operate in a certain relation to each other. When the machine is on rest, no centrifugal force is exercised by the centrifugal element 23, 25. Consequently the spring 24 forces the said element into the position in which the valve 22 is kept closed. Immediately upon starting the motor, when the same is rotating with its maximal number of revolutions because the lower part of the washing machine does not contain any liquid yet, the centrifugal force exercised by the element 23, 25 will outbalance the pressure emanating from the spring 24 so that the said element will dislocate itself outwards in the radial direction from the shaft 8, by which dislocation the channel 2i, 22 is opened. Liquid is now streaming through the channel l6, 2i, 22 into the interior of the lower part 2. Inasmuch as said lower part 2 is being filled with liquid, the motor i and together with it the shaft 5 are rotating more slowly because of the nature of the motor defined above. Consequently the centrifugal force exercised by the element 23, 25 is gradually decreasing whereas the counter-acting force from the spring 24 remains constant. Hereby the element 23, 25 is forced gradually to return to its initial position, by which movement the valve 23 is gradually throttled. As soon as the lower part 2 has been filled with liquid up to a certain level, for instance the level A, the number of revolutions of the motor i5 and the shaft 6 has sunk so much that the force from the spring 24 positively outbalances the centrifugal force exercised by the element 23, 25 which thus is forced back into its initial position in which the valve 23 is completely closed and the channel for permitting aillux of liquid positively blocked. The shovels I will then work in a constant amount of liquid which is circulated and thrown upwards over the dishes in the upper part i. .The tension of the spring 24 is adjustable by means of the bolted cap 26.

For the washing of glass a smaller amount of liquid is required than for the washing of china.

into the motor current circuit, for example in the level B indicated in Fig. 1. In this case the number of revolutions of the motor is and the shaft 2 must have decreased to that range where the force of the spring 24 positively outbalances the centrifugal force exercised by the element 22, 22 at a considerdably lower rotational speed than when washing china. In other words, the motor il must work with lower eflect when washing glass than when washing china, which result is suitably attained by switching in a particular resistance of control the manner diagrammatically indicated in Pig. 4. In this figure the series motor is designated by II. a resistance by 28 and a change-over switch by 30. when china is to be washed up said switch is adjusted to the position a in which the resistance 29 is by-passed and full current conducted to the motor I! so that its number of revolutions does not sink to the value causing the complete closing of the valve 22 but on reaching the level A of liquid supplied to the lower part 2 of the machine. When glass is to be washed up said switch is adjusted to the position b in which the resistance 29 is switched in and less current conducted to the motor I! so that its number of revolutions sinks to the value causing the complete closing of the valve 22 already when the'level B has been reached by the liquid supplied to the machine.

For the purpose of adjusting, the resistance 22 is suitably made variable. The same may be combined with a starter resistance though, as is well known, such starter resistance is dispensable in small series motors as will be used for washing machines of the type set forth.

while one more or less specific embodiment of the invention has been shown, it is to be understood that the same is for purpose of illustration only, and that the invention is not limited thereby, but its scope is to be determined by the appended claims viewed in the light of the prior art.

What I claim is:

l. A washing machine having an upper chamber for receiving articles to be washed, a lower chamber communicating with said upper chamber, an inlet for washing liquid connected to said lower chamber, a shaft in said louver, chamber carrying impelling members to circulate the liquid from the lower to the upper chamber, an electric motor for rotating said shaft, said motor being of the variable speed type varying in speed in accordance with the load on said impelling members determined by the amount of liquid in said lower chamber, rotatably mounted control means mounted to turn at a speed proportional to the speed of said shaft, said means including a valve in said inlet for closing the inlet when said shaft is at rest and to open the inlet in response to centrifugal force acting on said means when the motor is started and said impelling members are rotated in the absence of load from liquid in said lower chamber, said control means being constructed to cause said valve to progressively throttle said inlet as liquid is suppiied to said lower chamber with consequent increase in load on said impelling members and motor and reduction in speed thereof, until the inlet is closed upon reaching a liquid level in said lower chamber productive of a predetermined load and speed of said impellers and said motor.

2. A washing machine as claimed in claim 1, in which a variable resistance is arranged in the current circuit of the motor for selectively consupplied to the lower chamber until said control means close the liquid inlet.

3. A washing machine as claimed in claim 1, in which the shaft contains a channel attachable with its one end to a supply conduit of liquid and opening with its other end into the interior of the lower chamber of the machine through an opening controlled by the said valve.

4. A washing machine as claimed in claim 3, in which said control means includes a radially extending valve housing, said housing being secured to the shaft and communicating with the said channel as well as the lower chamber of the machine, and a valve body radially movable in said housing under the influence of centrifugal force and against the action of a spring member to control the liquid flowing through the said housing.

5. A washing machine as claimed in claim 4, in which the said spring member is inserted between said valve body and an adjustable cap SVEN BRJE FREDRIK CARLSTEDT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,696,677 Hayton Dec. 25, 1928 2,010,703 Slade et al. Aug. 6, 1935 2,022,220 Snyder Nov. 26, 1935 2,316,570 Dunham Apr. 13, 1943 

